The purpose of this project is to study the development of a range of spatial cognitive skills in 6-month to 4-year-old children with either right or left hemisphere focal brain injury to determine the extent to which spatial deficits can be documented in children with injuury to the right side of the brain. The project extends and elaborates the findings of an earlier study assessing children's block play, which identified, for the first time, a spatial constructive deficit in 2- and 3-year-olds with focal right hemisphere injury. The specific aims of this project are: First, to define more precisely the spatial constructive deficit identified previously, using tasks similar to the block play tasks used in the earlier study, but applying much more detail analytic measures; second, to examine drawing as a different kind of spatial constructive task to determine whether the deficit is specific to the organization of objects in space, or more general; and third, to extend the range of spatial cognitive assessment to the study of spatial perception. For all of the tasks, children will be followed longitudinally so that we can observe possible changes in behavior that might reflect functional recovery or development. Different methods will be used to assess spatial cognitive ability for the different tasks. The first involves a spontaneous block play task in which children are given small sets of toys and encouraged to play. Their play activities are videotaped, and later analyzed in detail for the kinds of spatial relations generated. The method for the drawing tasks in similar, except that children are asked to draw pictures of common objects, then both the pictures and the ways in which the children generated the pictures are assessed in detail. Spatial perception will be assessed differently according to the age of the children. Children under one year of age will be tested using versions of standard preference for novelty and object localization paradigms. Match-to-sample tasks will be used with 2- to 4-year-old children.